‘En Face' Optical Coherence Tomography with Enhanced Depth Imaging of Different Patterns of the Choroidal Neovascular Network in Age-Related Macular Degeneration

Abstract

The purpose of this study was to develop a method of segmentation using ‘en face' spectral domain-optical coherence tomography (SD-OCT) (‘en face' C-scans) to evaluate different patterns of the choroidal neovascular network (CNV) due to age-related macular degeneration (AMD). Materials and Method: A series of 90 patients with AMD comprising 30 cases of subfoveal fibrovascular pigment epithelial detachment, 15 cases of classic CNV and 35 cases of polypoidal choroidal vasculopathy. Fluorescein angiography, indocyanine green angiography and OCT (Spectralis, Heidelberg, Germany) images were analyzed. Volume acquisition of 97 enhanced depth imaging sections at 30-µm intervals was obtained, with a sum of 9 images for each retrofoveal scan. The image was superimposed on infrared and SLO ICG images to confirm the neovascularization. Results: Conventional SD-OCT only provides anteroposterior planes that only visualize the exudative reaction of the neovascular network. This new ‘en face' SD-OCT technology allows analysis of not only the contours and the shape of the detachment but also, and most importantly, visualizes the choroidal neovascular network in different patterns due to AMD. This imaging is obtained by means of an ‘en face' frontal mode with dynamic analysis in video or on frozen images, section by section, compared to standard SD-OCT or ICGA images with point-by-point correspondence. Conclusion: Until now, the CNV itself was not precisely detectable on conventional SD-OCT but only suggested by an exudative reaction. This new ‘en face' SD-OCT technology with dynamic segmentation of the macula allows to visualize the contours and the shape of the fibrovascular pigment epithelial detachment as well as the CNV in fibrovascular pigment epithelial detachment. SD-OCT can demonstrate direct signs of CNV within a pigment epithelial detachment and their localization, seen for the first time on OCT, without injection of dye in patients with a stable fixation point ‘en face' and will bring help for the easy detection of CNV and the decision for retreatment easier. ‘En face' OCT of classic CNV in AMD also allows to determine the origin of the CNV at the level of the choriocapillaris, the precise location of the ‘effraction' of the retinal pigment epithelium layer, the hyper-reflective course of type 2 CNV, in front of the retinal pigment epithelium and the correspondence between the CNV and the ‘intraretinal dense zones', and between ‘en face' OCT images and angiograms. ‘En face' OCT imaging of polypoidal choroidal vasculopathy allows analysis of the contours and number of polyps, visualization and localization of the abnormal choroidal network and their localization inside the (thickened) choroid, choriocapillaris and Bruch's membrane without the injection of a dye.